Abstract
With the development of urbanization,the construction of municipal underground pipeline is increasingly important.Based on the Hongxu-Hongmei rainwater pumping station and head pipe project,Flac 3D is employed to simulate and analyze the additional stress and surface deformation of surrounding soils caused by excavation in this paper.Then several examples are given to illustrate the influence of pipe jacking,which can help to understand the effect of construction process in more detail.In summary,this study results will benefit in-situ engineers to take suitable measures in real-life engineering.
The afore-mentioned numerical simulation of pipe jacking was widely carried out around the world,e.g.Huang and Hu[1]simulated the mechanical effect of pipe jacking.Fang et al.[2]focused on the difference between theoretical and measured analysis.Wei et al.[3]analyzed the soil disturbance during pipe jacking.
In order to fully reflect the influences of pipe jacking,this study mainly analyzed the lateral settlement,vertical settlement,plastic zone and support surface pressure.Furthermore,parameter sensitivity analysis during pipe jacking was also implemented.The results are as follows(Figure 1-Figure 6).
Figure 1 Lateral surface subsidence curve(Y=60 m)
Figure 2 Lateral displacement cloud map
Figure 3 Vertical surface subsidence curve(X=0)
Figure 4 Vertical displacement cloud map(X=0)
Figure 5 Transverse section of plastic zone of soil(Y=60 m)
Figure 6 Vertical section of plastic zone of soil(X=0)
Based on the simulation results,the following conclusions can be drawn.
(1)The curve of lateral subsidence trough is normally distributed,which is consistent with the Peck empirical formula.
(2)The results show that the trend of surface longitudinal settlement curve decreases gradually along the axis of the tube body,which obeys the distribution law of surface longitudinal settlement.
(3)The increase of support pressure will reduce the surface settlement in the excavation section,which mainly af fects the soil state within 2D distance from the central axis.However,too much support pressure may lead to the surface uplift in the trenchless section.
(4)Lateral friction mainly affects the disturbance of soil mass in the construction process.By reducing the lateral friction between the pipe and soil,the disturbance of soil can be effectively reduced and the fluctuation of surface settlement along the excavation axis can be reduced greatly.
Combined with the actual situation of the project and the numerical simulation results,it shows that increasing the support pressure properly and reducing the lateral friction resistance between the pipe and soil can ef fectively reduce the disturbance of the soil state and reduce the settlement.Therefore,it is important to control the support pressure reasonably,and reduce the lateral friction resistance in the construction process by using appropriate technology to control the surface settlement.